Effects of wastewater treatment plant pollution on in-stream ecosystems functions in an agricultural watershed

Abstract

-We studied the effect of point-source and non-point-source pollution on the retention capacity of the stream and its link with the metabolic state (primary production and respiration) and invertebrates assemblages in a third order Mediterranean stream. Two experimental sites were chosen: one in the upper part of the catchment (Monte´gut site) characterized by low concentrations in nitrate and phosphate and one in the lower part of the catchment (Le´zat site) characterized by high nitrate and phosphorus concentrations. Both experimental sites were located on reaches that included a Waste Water Treatment Plant (WWTP) point nutrient source allowing discussion of the relative effects of point-source and non-point-source nutrients loads on ecosystem function (respiration and uptake rates) and aquatic organism assemblages. NH 4 + -N, and PO 4 3x -P uptake rates were determined using solute additions conducted at constant rates (short-term nutrient addition procedure) and NO 3x -N uptake rates were determined using instantaneous solute addition (slug addition procedure). Rates of gross primary production (GPP) and ecosystem respiration were determined using the open system, two-stations diurnal oxygen change method. Benthic invertebrate communities were investigated for species and functional feeding groups diversities measurements. Results show that autotrophy in the river results from nutrients of two distinct origins: point sources for phosphorus (urban area and WWTP) and non-point sources for nitrogen (agricultural zones) with local additions from WWTP inputs.Comparison between the two sites shows that the WWTP did not affect uptake rates, respiration or primary production of the ecosystem in the low-nutrient Monte´gut reach despite increase of invertebrates communities biomass density. Inputs from the WWTP, in the high nitrate and phosphate Le´zat reach, increased respiration, lower benthic biomass and led to changes in the species composition and did not affect uptake rates.

Occurrence of metolachlor and trifluralin losses in the Save river agricultural catchment during floods

“…About 93% and 99% of metolachlor and trifluralin respectively entering the stream network does not reach the outlet, suggesting high deposition (discussed above) and degradation in stream water. The latter would be consistent with the carbon consumption by river biota shown by Sánchez-Pérez et al [55] on a similar catchment of Gascogne.…”

Identifying spatial and seasonal patterns of river water quality in a semiarid irrigated agricultural Mediterranean basin

“…These variables were related to sampling stations I6 and F6, which received inputs from the city of Huesca. Previous studies have reported that the primary source of P and NH 4 + -N are the urban inputs (Mendiguchía et al 2007;Neal et al 2000;Sánchez-Pérez et al 2009) and similarly for the case of NO 2 − -N (Martín-Queller et al 2010). Brainwood et al (2004) also observed that urban basins were highly correlated with NH 4 + ions and reactive PO 4 3− -P. Perona et al (1999) considered that in spring and summer, presence of holiday-makers leads to a high population density in the residential buildings and recreation areas influencing the nutrient content of the river.…”

Macroinvertebrate community traits and nitrate removal in stream sediments

“…() and applied by Ruggiero, Solimini, and Carchini () and Sánchez‐Pérez et al. (). The estimation of the stream nutrient retention rate for NO 3 − ‐N was made on each sampling date with a solute addition of a known quantity of nutrient (NO 3 − ‐N) into the stream.…”